Chapter 5 - Ducted propellers and fans

Summary

Introduction

A range of flow computational techniques has been developed over many years to meet the design and analysis requirements of a wide range of rotodynamic machines, some of which were illustrated by Fig. 4.1. For dealing with turbomachine meridional or through flows, which are usually completely confined within a continuous duct annulus such as that of the mixed-flow fan depicted in Fig. 4.1(a), surface vorticity or panel methods have been proved less attractive in competition with grid based analyses such as the matrix through-flow method of Wu (1952) and Marsh (1966) and the more recent time marching analyses such as those of Denton (1974), (1982). Although the annulus boundary shape exercises important control over the flow through the blade regions, in all turbomachines complex fluid dynamic processes occur throughout the whole flow field due to interactions between the S-1 and S-2 flows which were referred to in Chapter 3. Boundary integral methods based solely upon potential flow equations such as we have considered so far obviously cannot handle these interactions between the blade-to-blade and meridional flows, which involve detailed field calculations and spatial variations of properties best dealt with by the introduction of a grid strategically distributed throughout the annulus. Some attempts to achieve this with extended vortex boundary integral analysis will be outlined in Chapter 6, but generally speaking channel grid methods such as those referred to above have proved more fruitful to date for turbomachinery meridional analysis.